1. Field of the Invention
The invention relates to a circuit for the digital measuring of the difference in phase between a sequence of reference pulses, in particular a transmitted one, and a pulse sequence resulting as the output signal from a frequency divider for a clock signal whose frequency is higher by at least one order than that of the pulse sequence. Moreover, the invention relates to a use of this circuit for synchronizing the pulse sequence with the reference pulse sequence, as well as to a corresponding circuit arrangment.
2. Description of the Prior Art
The invention is particularly suitable for synchronizing the horizontal deflection in television receivers. In this particular case, the reference pulse sequence is represented by the transmitted horizontal sync pulses which, as is well known, are separated in the television receiver in the conventional way from the picture amplitude synchronizing signal. In respect to th so-called phase-locked oscillator circuits of the prior art, for example, in frequency synthesizers, phase-difference measuring plays a part. Such phase-locked oscillators consist of a frequency-controlled oscillator, a phase measuring circuit between the oscillator and reference signals, and a filter circuit for smoothing the control of the oscillator, using conventional analog techniques. Such filters are often relatively expensive and analog instrumentation is inherently susceptible to impreciseness because of noise.
It is possible to instrument phase measurement digitally, however, omnipresent noise pulses superimposed on the reference signal (received synchronizing pulse train (sequence) in the television case) tend to make the measurement imprecise.
The manner in which the invention deals with prior art disadvantages to produce a novel and effective digital phase measuring circuit (and synchronizer circuit) will be evident as the description proceeds.